Need help pairing speakers to mt amp

[MarineMike]

I have a kenwood KDC-HD545U deck wired to an Alpine MRP-F300 4 channel Amp pushing 4 Alpine SPS-507 speakers. One has busted and I was never able to crank the volume more than 2/3rds the way up without major distortion. I was wondering if anyone here would know the best 6x8 speakers to replace the Alpines so that I can turn it up as loud as I want and not have to worry about distortion, or busting my speakers. The amp pushes 50RMS per channel at 4ohms and 75 RMS at 2ohms. These are just for my highs as i have an Alpine MRP-M500 amp pushing 2 MTX Terminater 12's in a sealed box for my bass.

[Chris from Washington]

Where did you have the gain on your amp set at?

Rule of thumb is this to set it.
have the gain turned all the way down, turn the volume up to to close to max. Turn the gain up until the speakers start to distort, and then back it down to where you don't hear distortion.

What type of amp was it?